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DavidKomer
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how to read with supplyFile()?

Jul 10, 2012 4:24 AM

Short version:

I see there is an alchemy method called supplyFile(), but the second arg is a ByteArray... what in the world is that for?!?!

Longer version:

I would like to do the following:

  1. Open a file and assign it to a global variable on the C side of alchemy.
  2. Read in (and process) a chunk of bytes on the C side
  3. Send them to Actionscript for display
  4. Go to step 2 until EOF or notification from Actionscript
  5. Close the file

I'm able to do this right now by opening the file and reading the chunks into a ByteArray on the Actionscript side and then passing it to C for processing and back- but this calls some unnecessary overhead by needing to do AS3_ByteArray_writeBytes()/AS3_ByteArray_readBytes() on the C side in order to manipulate the data in a char *.

Is there any way to simply fopen() a file on the C side and read in some bytes? If not, will this be possible in alchemy 2?

Asssume we are talking about a very large file on disk (>4GB).

899 Views   6 Replies   Latest reply: Bruce_Jawn, Jul 11, 2012 3:38 AM
 
Replies
  • Bruce_Jawn
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    1. Bruce_Jawn,
    Jul 10, 2012 10:33 PM   in reply to DavidKomer
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    Here is a tutorial about this topic: http://blog.debit.nl/2009/03/using-bytearrays-in-actionscript-and-alch emy/

    You should first embed the file as a bytearray and "supply" it to alchemy, then you can use "fopen" directly on the C side.

    But I haven't tested that for large files.

     
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  • DavidKomer
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    2. DavidKomer,
    Jul 10, 2012 11:17 PM   in reply to Bruce_Jawn
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    Thanks Bruce- but please see what I wrote: "I'm able to do this right now by opening the file and reading the chunks into a ByteArray on the Actionscript side and then passing it to C for processing and back- but this calls some unnecessary overhead"

     

    Note that I'm also chasing this down via stackoverflow, please see my comments there which illustrate the problem in a little more depth: http://stackoverflow.com/questions/11398559/how-to-read-with-supplyfil e

     

    Any ideas anyone? Will this be solved in alchemy2?!

     
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  • DavidKomer
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    3. DavidKomer,
    Jul 10, 2012 11:19 PM   in reply to DavidKomer
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    To be clear, here's my specific comment which sums the problem up another way: "I've already had to do one read (in Actionscript) to get the data from the file into a ByteArray. Is another fread() or AS3_ByteArray_readBytes() really necessary just to work with the data on the C side?"

     
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  • Bruce_Jawn
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    4. Bruce_Jawn,
    Jul 11, 2012 2:06 AM   in reply to DavidKomer
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    Maybe you can use domain memory API to avoid using "supplyFile" and function calls like that. That's the trick used a lot in many alchemy projects for passing and returning frame buffers. See the source code of the example: http://unitzeroone.com/blog/2009/04/06/more-play-with-alchemy-lookup-t able-effects/

     
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  • DavidKomer
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    5. DavidKomer,
    Jul 11, 2012 2:54 AM   in reply to Bruce_Jawn
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    I am using the domain memory API to avoid using "supplyFile" etc... but the link you showed highlighted a point I missed... the domain memory is actually seen as a ByteArray on the actionscript side. So it's maybe possible to FileStream.readBytes() directly into the domain memory space by allocating the pointer as a char * on the C side, passing that pointer to the actionscript side, and reading it directly into that pointer (an offset of AS3_Ram())

     

    Thankfully, I've been able to join up the alchemy 2 pre-release now, so I'm not going to test this out on alchemy 1 at the moment, but maybe this is of use to someone else- and thanks for your help, Bruce!

     
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  • Bruce_Jawn
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    6. Bruce_Jawn,
    Jul 11, 2012 3:38 AM   in reply to DavidKomer
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    BTW, Alchemy1's API is not available in Alchemy2, so the above trick can't be used in Alchemy2 any more the same way as in Alchmey1.

     
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